It isn't the water pH so much as the mash pH or the ability of the grains to bring the water in the range of 5.2 to 5.4. You really need a way to check the mash pH to know. On my last batch, a porter which should be capable of bringing most water to that range, with my water I mashed in at 6.0. As long as I kept the temperature lower than about 170 that would still make good beer but since I had the meter and the acid blend, I added acid blend to make it 5.3. Unless you know that your mash pH was too high and that you caused the temperature to rise over 170 during mashout or sparging, I wouldn't worry too much.